The Transparent Interconnection of Lots of Link (TRILL) technology is a technology integrating advantages of the layer 2 technology and the layer 3 technology, which applies the Intermediate System to Intermediate System (ISIS) link state routing protocol to calculate a topology of a layer 2 network, solves the problem that paths of the layer 2 network cannot be fully used because execution of the Rapid Spanning Tree Protocol (STP) in a layer 2 bridge needs to block some links, and provides load balancing of the link through the Equal-Cost Multipath Routing (ECMP) algorithm. The TRILL protocol solves the problem of loop by employing the idea of the shortest path and the minimum hop count of route while avoiding large oscillation of network under the STP network condition after failure appears, and applies the idea of distribution tree to solve the problem of multicast transmission and broadcast transmission while ensuring and simplifying the processing of a multicast message by learning pruning, backward path detection and other ways of the routing protocol. An ingress routing bridge is set at the ingress of the TRILL network, which completes a TRILL encapsulation of original data, wherein unicast data is forwarded along the shortest path calculated by the Shortest Path First (SPF) algorithm, and multicast data or broadcast data are forwarded to multiple egresses along the distribution tree. An egress routing bridge is also set in the TRILL network, which performs de-encapsulation on a TRILL message.
The TRILL protocol introduces a new namespace with length of 16 bits, which is called nickname and encapsulated into the TRILL message header; for a middle transmission routing bridge, it is only needed to look up a nickname table according to a destination nickname to forward data. Since the length of nickname is only 16 bits at the beginning of design, with the expansion of data centre, especially with the proposition of cloud computing data centre, the length of nickname may become a bottleneck in the future. In addition, for an edge routing bridge, it is needed to save a mapping relationship between a Media Access Control (MAC) address and the nickname; when the network size is very large, the amount of the entry mapping relationships is relatively large, so a method for distributing the nickname to terminal users is provided in the industry, in which the terminal users save a part of mapping entries, and a nickname value encapsulated by a terminal is the nickname value used by the routing bridge to which the terminal is adhered, thereby being capable of reducing the size of a mapping table of the edge routing bridge without taking the space of nickname. The terminal which can perform TRILL encapsulation is called smart terminal.
For unicast data, when the edge routing bridge finds that the destination address of data is a smart terminal adhered to the edge routing bridge, the edge routing bridge maintains the TRILL encapsulation of the message without need of de-encapsulation, and directly forwards the message to the destination smart terminal; the destination smart terminal performs de-encapsulation and address learning after receiving the TRILL message.
However, for multicast data, since the terminals adhered to the edge routing bridge may include smart terminals and ordinary terminals (namely the terminals which cannot perform encapsulation and de-encapsulation on the TRILL message), if the edge routing bridge maintains the TRILL encapsulation, then the ordinary terminal cannot parse the multicast data, and the common multicast communication cannot be performed between a remote terminal and the ordinary terminal. If the edge routing bridge performs de-encapsulation on the TRILL message, and forwards the original message to the terminal adhered to the routing bridge, then the smart terminal cannot learn mapping information of an opposite-side terminal, thereby disabling the normal communication between the smart terminals.